https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70196
--- Comment #4 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
ordering comparison of pointers is only well-defined when the two pointers
point into the same object (including one-past-the-end). [expr.ref]/4
No object can have a NULL address.
The third bullet permits a compiler to /always/ return true (or false) for any
stricly ordered relational pointer comparison involving a null pointer
constant. (AFAICT even '(void *)0 < 0' is included in that). The -or-equal
operators coult be expanded to '(strict-order) | (equality-cmp)', and then
simplified based on what constant we chose the strict-order to always return.
Now, that said, I think the problematic statement in the example is:
constexpr int *q = &i;
That should probably be rejected, as it assigns the set {NULL, obj-addr} to q.
